1. Field
Example embodiments relate to a multi-chip package for a light-emitting diode (LED) and a LED device including the multi-chip package, and more particularly, to a LED multi-chip package in which a plurality of LED chips may be disposed within a single package, and a LED device including the multi-chip package.
2. Description of the Related Art
Light-emitting diodes (LED) have undergone significant developments since the early 1990s using nitride semiconductor thin-films, and most short wavelength LEDs now use nitride semiconductor thin-films. Specifically, developments in semiconductor growth technologies and device fabricating technologies have improved efficiency of LEDs using the nitride semiconductor thin-films. As a result, nitride-based semiconductor LEDs may be applied to various fields, e.g., light sources of display devices, optical communications, or illuminations. Recently, a nitride-based semiconductor LED having an efficiency of about 120 lm/W or higher has been developed. Such nitride-based semiconductor LEDs have sufficient efficiency to replace conventional light sources, e.g., lamps.
Recently, due to the above-described developments in LEDs, light sources using LEDs are being developed for home lighting, decorative lighting, or display lighting. LEDs, energy-conserving and environmentally conscious light sources, are regarded as next-generation light sources for lighting. Thus, LEDs are being developed to replace conventional light sources. To use LEDs for lighting, LEDs are required to emit light having the same brightness as conventional light sources. Thus, research is being devoted to improving efficiency of LEDs simultaneously with applying high power to LEDs such that the LEDs emit bright light. Currently, higher power and higher brightness LEDs are being developed with a goal of obtaining light of about 1,000 lumens per LED chip.
However, a problem of such an approach may be applying increased power to a single chip of a LED device for lighting. When relatively high power is applied to a single LED chip, overall light brightness increases. However, light emitting efficiency decreases and heat corresponding to the efficiency loss is generated. Thus, applying increased power to a single LED chip is regarded as a cause of either decreasing the lifespan of the LED chip or diminishing reliability of the LED chip.
Furthermore, to control the generated heat, a cooling fan and a heat sink are required to be included in a LED device for lighting. Thus, the manufacturing costs and the volume of a LED device for lighting increase. Furthermore, LED devices for lighting currently in use are relatively small, and thus, are basically point light sources. This characteristic may not satisfy the requirements for surface light emission.
Generally, the brightness of light emitted by a LED device depends on the amount of power applied to the LED device. Specifically, the driving voltage of a LED device may be between about 3.0 V and about 3.5 V regardless of the size of the LED device. Thus, the brightness of light emitted by the LED device varies according to the electric current applied to the LED device. For example, the brightness of light emitted by the LED increases in proportion to the magnitude of electrical current applied to the LED. However, light emitting efficiency of the LED device may be at its peak when the electric current applied to the LED device is between about 5 mA and about 10 mA, and decreases as the electric current applied to the LED device increases.
In most cases, an electrical current of about 350 mA or more may be applied to high power and high brightness LEDs currently in use for increasing brightness. As a result, light emitting efficiency may be relatively low. Furthermore, part of the applied electric current corresponding to decrease of the light emitting efficiency may be converted to heat, and thus the temperature of a LED chip increases. Therefore, as described above, heat dissipating measures for dissipating heat generated by a LED chip to the outside may be required for conventional LED devices, e.g. heat sinks.
To obtain a LED device with lower heat generation and higher light emitting efficiency, driving a LED device by applying an electrical current corresponding to the maximum light emitting efficiency may be required. However, the brightness of light emitted by the LED may decrease.